System and method for providing an InfiniBand SR-IOV vSwitch architecture for a high performance cloud computing environment

ABSTRACT

Systems and methods are provided for implementing a Virtual Switch (vSwitch) architecture that supports transparent virtualization and live migration. In an embodiment, a vSwitch with prepopulated Local Identifiers (LIDs). Another embodiment provides for vSwitch with dynamic LID assignment. Another embodiment provides for vSwitch with prepopulated LIDS and dynamic LID assignment. Moreover, embodiments of the present invention provide scalable dynamic network reconfiguration methods which enable live migrations of VMs in network environments.

CLAIM OF PRIORITY AND CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of and claims priority to of U.S.Patent Application “SYSTEM AND METHOD FOR PROVIDING AN INFINIBAND SR-IOVvSWITCH ARCHITECTURE FOR A HIGH PERFORMANCE COMPUTING ENVIRONMENT”,application Ser. No. 15/993,266, filed on May 30, 2018, whichapplication is a continuation of and claims priority to U.S. PatentApplication “SYSTEM AND METHOD FOR PROVIDING AN INFINIBAND SR-IOVvSWITCH ARCHITECTURE FOR A HIGH PERFORMANCE COMPUTING ENVIRONMENT”,application Ser. No. 15/050,901, filed Feb. 23, 2016, which claims thebenefit of priority to U.S. Provisional Patent Application entitled“SYSTEM AND METHOD FOR PROVIDING AN INFINIBAND SR-IOV vSWITCHARCHITECTURE FOR A HIGH PERFORMANCE COMPUTING ENVIRONMENT”, ApplicationNo. 62/129,273, filed on Mar. 6, 2015, and to U.S. Provisional PatentApplication entitled “SYSTEM AND METHOD FOR PROVIDING AN INFINIBANDSR-IOV vSWITCH ARCHITECTURE FOR A HIGH PERFORMANCE COMPUTINGENVIRONMENT”, Application No. 62/161,078, filed on May 13, 2015; thisapplication is related to U.S. Patent Application entitled “SYSTEM ANDMETHOD FOR SUPPORTING LIVE MIGRATION OF VIRTUAL MACHINES IN ANINFINIBAND NETWORK”, application Ser. No. 13/837,922, filed Mar. 15,2013; U.S. Patent Application entitled “SYSTEM AND METHOD FOR SUPPORTINGLIVE MIGRATION OF VIRTUAL MACHINES IN A VIRTUALIZATION ENVIRONMENT,”application Ser. No. 13/838,121, filed Mar. 15, 2013; U.S. PatentApplication entitled “SYSTEM AND METHOD FOR SUPPORTING LIVE MIGRATION OFVIRTUAL MACHINES BASED ON AN EXTENDED HOST CHANNEL ADAPTOR (HCA) MODEL,”application Ser. No. 13/838,275, filed Mar. 15, 2013; and U.S. PatentApplication entitled “SYSTEM AND METHOD FOR PROVIDING A SCALABLESIGNALING MECHANISM FOR VIRTUAL MACHINE MIGRATION IN A MIDDLEWAREMACHINE ENVIRONMENT,” application Ser. No. 13/838,502, filed Mar. 15,2013, which applications are herein incorporated by reference in theirentirety.

COPYRIGHT NOTICE

A portion of the disclosure of this patent document contains materialwhich is subject to copyright protection. The copyright owner has noobjection to the facsimile reproduction by anyone of the patent documentor the patent disclosure, as it appears in the Patent and TrademarkOffice patent file or records, but otherwise reserves all copyrightrights whatsoever.

FIELD OF INVENTION

The present invention is generally related to computer systems, and isparticularly related to supporting computer system virtualization andlive migration using SR-IOV vSwitch architecture.

BACKGROUND

As larger cloud computing architectures are introduced, the performanceand administrative bottlenecks associated with the traditional networkand storage have become a significant problem. There has been anincreased interest in using InfiniBand (IB) technology as the foundationfor a cloud computing fabric. This is the general area that embodimentsof the invention are intended to address.

SUMMARY

Described herein are systems and methods for supporting virtual machinemigration in a subnet. An exemplary method can provide, at one or morecomputers, including one or more microprocessors, one or more switches,the one or more switches comprising at least a leaf switch, wherein eachof the one or more switches comprise a plurality of ports, a pluralityof host channel adapters, wherein the plurality of host channel adaptersare interconnected via the one or more switches, a plurality ofhypervisors, wherein each of the plurality of hypervisors are associatedwith one of the plurality of host channel adapters, and a plurality ofvirtual machines. The method can further arrange the plurality of hostchannel adapters with one or more of a virtual switch with prepopulatedlocal identifiers (LIDs) architecture or a virtual switch with dynamicLID assignment architecture. The method can additionally live migrate afirst virtual machine of the plurality of virtual machines running on afirst hypervisor of the plurality of hypervisors to a second hypervisorof the plurality of hypervisors; and wherein the first hypervisor isassociated with a first host channel adapter of the plurality of hostchannel adapters, and the second hypervisor is associated with a secondhost channel adapter of the plurality of host channel adapters.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 shows an illustration of an InfiniBand environment, in accordancewith an embodiment.

FIG. 2 shows an illustration of a tree topology in a networkenvironment, accordance with an embodiment.

FIG. 3 shows an exemplary shared port architecture, in accordance withan embodiment.

FIG. 4 shows an exemplary vSwitch architecture, in accordance with anembodiment.

FIG. 5 shows an exemplary vSwitch architecture with prepopulated LIDs,in accordance with an embodiment.

FIG. 6 shows an exemplary vSwitch architecture with dynamic LIDassignment, in accordance with an embodiment.

FIG. 7 shows an exemplary vSwitch architecture with vSwitch with dynamicLID assignment and prepopulated LIDs, in accordance with an embodiment.

FIG. 8 shows an exemplary vSwitch architecture with prepopulated LIDsprior to a virtual machine migration, in accordance with an embodiment.

FIG. 9 shows an exemplary vSwitch architecture with prepopulated LIDsafter a virtual machine migration, in accordance with an embodiment.

FIG. 10 shows an exemplary vSwitch architecture with prepopulated LIDswith potential virtual machine migration paths, in accordance with anembodiment.

FIG. 11 is a flow chart of a method for supporting virtual machinemigration in a subnet, in accordance with an embodiment.

DETAILED DESCRIPTION

The invention is illustrated, by way of example and not by way oflimitation, in the figures of the accompanying drawings in which likereferences indicate similar elements. It should be noted that referencesto “an” or “one” or “some” embodiment(s) in this disclosure are notnecessarily to the same embodiment, and such references mean at leastone. While specific implementations are discussed, it is understood thatthe specific implementations are provided for illustrative purposesonly. A person skilled in the relevant art will recognize that othercomponents and configurations may be used without departing from thescope and spirit of the invention.

Common reference numerals can be used to indicate like elementsthroughout the drawings and detailed description; therefore, referencenumerals used in a figure may or may not be referenced in the detaileddescription specific to such figure if the element is describedelsewhere.

Described herein are systems and methods that can support virtualmachine (VM) migration in a network.

The following description of the invention uses an InfiniBand™ (IB)network as an example for a high performance network. It will beapparent to those skilled in the art that other types of highperformance networks can be used without limitation. The followingdescription also uses the fat-tree topology as an example for a fabrictopology. It will be apparent to those skilled in the art that othertypes of fabric topologies can be used without limitation.

In accordance with an embodiment of the invention, virtualization can bebeneficial to efficient resource utilization and elastic resourceallocation in cloud computing. Live migration makes it possible tooptimize resource usage by moving virtual machines (VMs) betweenphysical servers in an application transparent manner. Thus,virtualization can enable consolidation, on-demand provisioning ofresources, and elasticity through live migration.

InfiniBand™

InfiniBand™ (IB) is an open standard lossless network technologydeveloped by the InfiniBand™ Trade Association. The technology is basedon a serial point-to-point full-duplex interconnect that offers highthroughput and low latency communication, geared particularly towardshigh-performance computing (HPC) applications and datacenters.

The InfiniBand™ Architecture (IBA) supports a two-layer topologicaldivision. At the lower layer, IB networks are referred to as subnets,where a subnet can include a set of hosts interconnected using switchesand point-to-point links. At the higher level, an IB fabric constitutesone or more subnets, which can be interconnected using routers.

Within a subnet, hosts can be connected using switches andpoint-to-point links. Additionally, there can be a master managemententity, the subnet manager (SM), which resides on a designated subnetdevice in the subnet. The subnet manager is responsible for configuring,activating and maintaining the IB subnet. Additionally, the subnetmanager (SM) can be responsible for performing routing tablecalculations in an IB fabric. Here, for example, the routing of the IBnetwork aims at proper load balancing between all source and destinationpairs in the local subnet.

Through the subnet management interface, the subnet manager exchangescontrol packets, which are referred to as subnet management packets(SMPs), with subnet management agents (SMAs). The subnet managementagents reside on every IB subnet device. By using SMPs, the subnetmanager is able to discover the fabric, configure end nodes andswitches, and receive notifications from SMAs.

In accordance with an embodiment, inter- and intra-subnet routing in anIB network can be based on LFTs stored in the switches. The LFTs arecalculated by the SM according to the routing mechanism in use. In asubnet, Host Channel Adapter (HCA) ports on the end nodes and switchesare addressed using local identifiers (LIDs). Each entry in an LFTconsists of a destination LID (DLID) and an output port. Only one entryper LID in the table is supported. When a packet arrives at a switch,its output port is determined by looking up the DLID in the forwardingtable of the switch. The routing is deterministic as packets take thesame path in the network between a given source-destination pair (LIDpair).

Generally, all other subnet managers, excepting the master subnetmanager, act in standby mode for fault-tolerance. In a situation where amaster subnet manager fails, however, a new master subnet manager isnegotiated by the standby subnet managers. The master subnet manageralso performs periodic sweeps of the subnet to detect any topologychanges and reconfigure the network accordingly.

Furthermore, hosts and switches within a subnet can be addressed usinglocal identifiers (LIDs), and a single subnet can be limited to 49151unicast LIDs. Besides the LIDs, which are the local addresses that arevalid within a subnet, each IB device can have a 64-bit global uniqueidentifier (GUID). A GUID can be used to form a global identifier (GID),which is an IB layer three (L3) address.

The SM can calculate routing tables (i.e., the connections/routesbetween each pair of nodes within the subnet) at network initializationtime. Furthermore, the routing tables can be updated whenever thetopology changes, in order to ensure connectivity and optimalperformance. During normal operations, the SM can perform periodic lightsweeps of the network to check for topology changes. If a change isdiscovered during a light sweep or if a message (trap) signaling anetwork change is received by the SM, the SM can reconfigure the networkaccording to the discovered changes.

For example, the SM can reconfigure the network when the networktopology changes, such as when a link goes down, when a device is added,or when a link is removed. The reconfiguration steps can include thesteps performed during the network initialization. Furthermore, thereconfigurations can have a local scope that is limited to the subnets,in which the network changes occurred. Also, the segmenting of a largefabric with routers may limit the reconfiguration scope.

In accordance with an embodiment, IB networks can support partitioningas a security mechanism to provide for isolation of logical groups ofsystems sharing a network fabric. Each HCA port on a node in the fabriccan be a member of one or more partitions. Partition memberships aremanaged by a centralized partition manager, which can be part of the SM.The SM can configure partition membership information on each port as atable of 16-bit partition keys (P Keys). The SM can also configureswitches and routers with the partition enforcement tables containing PKey information associated with the LIDs. Additionally, in a generalcase, partition membership of a switch port can represent a union of allmembership indirectly associated with LIDs routed via the port in anegress (towards the link) direction.

In accordance with an embodiment, for the communication between nodes,Queue Pairs (QPs) and End-to-End contexts (EECs) can be assigned to aparticular partition, except for the management Queue Pairs (QP0 andQP1). The P Key information can then be added to every IB transportpacket sent. When a packet arrives at an HCA port or a switch, its P Keyvalue can be validated against a table configured by the SM. If aninvalid P Key value is found, the packet is discarded immediately. Inthis way, communication is allowed only between ports sharing apartition.

An example InfiniBand fabric is shown in FIG. 1, which shows anillustration of an InfiniBand environment 100, in accordance with anembodiment. In the example shown in FIG. 1, nodes A-E, 101-105, use theInfiniBand fabric, 120, to communicate, via the respective host channeladapters 111-115. In accordance with an embodiment, the various nodes,e.g., nodes A-E, 101-105, can be represented by various physicaldevices. In accordance with an embodiment, the various nodes, e.g.,nodes A-E, 101-105, can be represented by various virtual devices, suchas virtual machines.

Virtual Machines in InfiniBand

During the last decade, the prospect of virtualized High PerformanceComputing (HPC) environments has improved considerably as CPU overheadhas been practically removed through hardware virtualization support;memory overhead has been significantly reduced by virtualizing theMemory Management Unit; storage overhead has been reduced by the use offast SAN storages or distributed networked file systems; and network I/Ooverhead has been reduced by the use of device passthrough techniqueslike Single Root Input/Output Virtualization (SR-IOV). It is nowpossible for clouds to accommodate virtual HPC (vHPC) clusters usinghigh performance interconnect solutions and deliver the necessaryperformance.

However, when coupled with lossless networks, such as InfiniBand (IB),certain cloud functionality, such as live migration of virtual machines(VMs), still remains an issue due to the complicated addressing androuting schemes used in these solutions. IB is an interconnectionnetwork technology offering high bandwidth and low latency, thus, isvery well suited for HPC and other communication intensive workloads.

The traditional approach for connecting IB devices to VMs is byutilizing SR-IOV with direct assignment. However, to achieve livemigration of VMs assigned with IB Host Channel Adapters (HCAs) usingSR-IOV has proved to be challenging. Each IB connected node has threedifferent addresses: LID, GUID, and GID. When a live migration happens,one or more of these addresses change. Other nodes communicating withthe VM-in-migration can lose connectivity. When this happens, the lostconnection can be attempted to be renewed by locating the virtualmachine's new address to reconnect to by sending Subnet Administration(SA) path record queries to the IB Subnet Manager (SM).

IB uses three different types of addresses. A first type of address isthe 16 bits Local Identifier (LID). At least one unique LID is assignedto each HCA port and each switch by the SM. The LIDs are used to routetraffic within a subnet. Since the LID is 16 bits long, 65536 uniqueaddress combinations can be made, of which only 49151 (0x0001-0xBFFF)can be used as unicast addresses. Consequently, the number of availableunicast addresses defines the maximum size of an IB subnet. A secondtype of address is the 64 bits Global Unique Identifier (GUID) assignedby the manufacturer to each device (e.g. HCAs and switches) and each HCAport. The SM may assign additional subnet unique GUIDs to an HCA port,which is useful when SR-IOV is used. A third type of address is the 128bits Global Identifier (GID). The GID is a valid IPv6 unicast address,and at least one is assigned to each HCA port. The GID is formed bycombining a globally unique 64 bits prefix assigned by the fabricadministrator, and the GUID address of each HCA port.

Fat-Tree (FTree) Topologies and Routing

In accordance with an embodiment, some of the IB based HPC systemsemploy a fat-tree topology to take advantage of the useful propertiesfat-trees offer. These properties include full bisection-bandwidth andinherent fault-tolerance due to the availability of multiple pathsbetween each source destination pair. The initial idea behind fat-treeswas to employ fatter links between nodes, with more available bandwidth,as the tree moves towards the roots of the topology. The fatter linkscan help to avoid congestion in the upper-level switches and thebisection-bandwidth is maintained.

FIG. 2 shows an illustration of a tree topology in a networkenvironment, in accordance with an embodiment. As shown in FIG. 2, oneor more end nodes 201-204 can be connected in a network fabric 200. Thenetwork fabric 200 can be based on a fat-tree topology, which includes aplurality of leaf switches 211-214, and multiple spine switches or rootswitches 231-234. Additionally, the network fabric 200 can include oneor more intermediate switches, such as switches 221-224.

Also as shown in FIG. 2, each of the end nodes 201-204 can be amulti-homed node, i.e., a single node that is connected to two or moreparts of the network fabric 200 through multiple ports. For example, thenode 201 can include the ports H1 and H2, the node 202 can include theports H3 and H4, the node 203 can include the ports H5 and H6, and thenode 204 can include the ports H7 and H8.

Additionally, each switch can have multiple switch ports. For example,the root switch 231 can have the switch ports 1-2, the root switch 232can have the switch ports 3-4, the root switch 233 can have the switchports 5-6, and the root switch 234 can have the switch ports 7-8.

In accordance with an embodiment, the fat-tree routing mechanism is oneof the most popular routing algorithm for IB based fat-tree topologies.The fat-tree routing mechanism is also implemented in the OFED (OpenFabric Enterprise Distribution—a standard software stack for buildingand deploying IB based applications) subnet manager, OpenSM.

The fat-tree routing mechanism aims to generate LFTs that evenly spreadshortest-path routes across the links in the network fabric. Themechanism traverses the fabric in the indexing order and assigns targetLIDs of the end nodes, and thus the corresponding routes, to each switchport. For the end nodes connected to the same leaf switch, the indexingorder can depend on the switch port to which the end node is connected(i.e., port numbering sequence). For each port, the mechanism canmaintain a port usage counter, and can use this port usage counter toselect a least-used port each time a new route is added.

As mentioned above, in a partitioned subnet, nodes that are not membersof a common partition are not allowed to communicate. Practically, thismeans that some of the routes assigned by the fat-tree routing algorithmare not used for the user traffic. The problem arises when the fat treerouting mechanism generates LFTs for those routes the same way it doesfor the other functional paths. This behavior can result in degradedbalancing on the links, as nodes are routed in the order of indexing. Asrouting is done oblivious to the partitions, fat-tree routed subnets, ingeneral, provide poor isolation among partitions.

Input/Output (I/O) Virtualization

In accordance with an embodiment, I/O Virtualization (IOV) can provideavailability of I/O by allowing virtual machines (VMs) to access theunderlying physical resources. The combination of storage traffic andinter-server communication impose an increased load that may overwhelmthe I/O resources of a single server, leading to backlogs and idleprocessors as they are waiting for data. With the increase in number ofI/O requests, IOV can provide availability; and can improve performance,scalability and flexibility of the (virtualized) I/O resources to matchthe level of performance seen in modern CPU virtualization.

In accordance with an embodiment, IOV is desired as it can allow sharingof I/O resources and provide protected access to the resources from theVMs. IOV decouples a logical device, which is exposed to a VM, from itsphysical implementation. Currently, there can be different types of IOVtechnologies, such as emulation, paravirtualization, direct assignment(DA), and single root-I/O virtualization (SR-IOV).

In accordance with an embodiment, one type of IOV technology is softwareemulation. Software emulation can allow for a decoupledfront-end/back-end software architecture. The front-end can be a devicedriver placed in the VM, communicating with the back-end implemented bya hypervisor to provide I/O access. The physical device sharing ratio ishigh and live migrations of VMs are possible with just a fewmilliseconds of network downtime. However, software emulation introducesadditional, undesired computational overhead.

In accordance with an embodiment, another type of IOV technology isdirect device assignment. Direct device assignment involves a couplingof I/O devices to VMs, with no device sharing between VMs. Directassignment, or device passthrough, provides near to native performancewith minimum overhead. The physical device bypasses the hypervisor andis directly attached to the VM. However, a downside of such directdevice assignment is limited scalability, as there is no sharing amongvirtual machines—one physical network card is coupled with one VM.

In accordance with an embodiment, Single Root IOV (SR-IOV) can allow aphysical device to appear through hardware virtualization as multipleindependent lightweight instances of the same device. These instancescan be assigned to VMs as passthrough devices, and accessed as VirtualFunctions (VFs). The hypervisor accesses the device through a unique(per device), fully featured Physical Function (PF). SR-IOV eases thescalability issue of pure direct assignment. However, a problempresented by SR-IOV is that it can impair VM migration. Among these IOVtechnologies, SR-IOV can extend the PCI Express (PCIe) specificationwith the means to allow direct access to a single physical device frommultiple VMs while maintaining near to native performance. Thus, SR-IOVcan provide good performance and scalability.

SR-IOV allows a PCIe device to expose multiple virtual devices that canbe shared between multiple guests by allocating one virtual device toeach guest. Each SR-IOV device has at least one physical function (PF)and one or more associated virtual functions (VF). A PF is a normal PCIefunction controlled by the virtual machine monitor (VMM), or hypervisor,whereas a VF is a light-weight PCIe function. Each VF has its own baseaddress (BAR) and is assigned with a unique requester ID that enablesI/O memory management unit (IOMMU) to differentiate between the trafficstreams to/from different VFs. The IOMMU also apply memory and interrupttranslations between the PF and the VFs.

Unfortunately, however, direct device assignment techniques pose abarrier for cloud providers in situations where transparent livemigration of virtual machines is desired for data center optimization.The essence of live migration is that the memory contents of a VM arecopied to a remote hypervisor. Then the VM is paused at the sourcehypervisor, and the VM's operation is resumed at the destination. Whenusing software emulation methods, the network interfaces are virtual sotheir internal states are stored into the memory and get copied as well.Thus the downtime could be brought down to a few milliseconds.

However, migration becomes more difficult when direct device assignmenttechniques, such as SR-IOV, are used. In such situations, a completeinternal state of the network interface cannot be copied as it is tiedto the hardware. The SR-IOV VFs assigned to a VM are instead detached,the live migration will run, and a new VF will be attached at thedestination. In the case of InfiniBand and SR-IOV, this process canintroduce downtime in the order of seconds. Moreover, in an SR-IOVshared port model the addresses of the VM will change after themigration, causing additional overhead in the SM and a negative impacton the performance of the underlying network fabric.

InfiniBand SR-IOV Architecture—Shared Port

There can be different types of SR-IOV models, e.g. a shared port modeland a virtual switch model.

FIG. 3 shows an exemplary shared port architecture, in accordance withan embodiment. As depicted in the figure, a host 300 (e.g., a hostchannel adapter) can interact with a hypervisor 310, which can assignthe various virtual functions 330, 340, 350, to a number of virtualmachines. As well, the physical function can be handled by thehypervisor 310.

In accordance with an embodiment, when using a shared port architecture,such as that depicted in FIG. 3, the host, e.g., HCA, appears as asingle port in the network with a single shared LID and shared QueuePair (QP) space between the physical function 320 and the virtualfunctions 330, 350, 350. However, each function (i.e., physical functionand virtual functions) can have their own GID.

As shown in FIG. 3, in accordance with an embodiment, different GIDs canbe assigned to the virtual functions and the physical function, and thespecial queue pairs, QP0 and QP1 (i.e., special purpose queue pairs thatare used for InfiniBand management packets), are owned by the physicalfunction. These QPs are exposed to the VFs as well, but the VFs are notallowed to use QP0 (all SMPs coming from VFs towards QP0 are discarded),and QP1 can act as a proxy of the actual QP1 owned by the PF.

In accordance with an embodiment, the shared port architecture can allowfor highly scalable data centers that are not limited by the number ofVMs (which attach to the network by being assigned to the virtualfunctions), as the LID space is only consumed by physical machines andswitches in the network.

However, a shortcoming of the shared port architecture is the inabilityto provide transparent live migration, hindering the potential forflexible VM placement. As each LID is associated with a specifichypervisor, and shared among all VMs residing on the hypervisor, amigrating VM (i.e., a virtual machine migrating to a destinationhypervisor) has to have its LID changed to the LID of the destinationhypervisor. Furthermore, as a consequence of the restricted QP0 access,a subnet manager cannot run inside a VM.

InfiniBand SR-IOV Architecture Models—Virtual Switch (vSwitch)

There can be different types of SR-IOV models, e.g. a shared port modeland a virtual switch model.

FIG. 4 shows an exemplary vSwitch architecture, in accordance with anembodiment. As depicted in the figure, a host 400 (e.g., a host channeladapter) can interact with a hypervisor 410, which can assign thevarious virtual functions 430, 440, 450, to a number of virtualmachines. As well, the physical function can be handled by thehypervisor 410. A virtual switch 415 can also be handled by thehypervisor 401.

In accordance with an embodiment, in a vSwitch architecture each virtualfunction 430, 440, 450 is a complete virtual Host Channel Adapter(vHCA), meaning that the VM assigned to a VF is assigned a complete setof IB addresses (e.g., GID, GUID, LID) and a dedicated QP space in thehardware. For the rest of the network and the SM, the HCA 400 looks likea switch, via the virtual switch 415, with additional nodes connected toit. The hypervisor 410 can use the PF 420, and the VMs (attached to thevirtual functions) use the VFs.

In accordance with an embodiment, a vSwitch architecture providetransparent virtualization. However, because each virtual function isassigned a unique LID, the number of available LIDs gets consumedrapidly. As well, with many LID addresses in use (i.e., one each foreach physical function and each virtual function), more communicationpaths have to be computed by the SM and more Subnet Management Packets(SMPs) have to be sent to the switches in order to update their LFTs.For example, the computation of the communication paths might takeseveral minutes in large networks. Because LID space is limited to 49151unicast LIDs, and as each VM (via a VF), physical node, and switchoccupies one LID each, the number of physical nodes and switches in thenetwork limits the number of active VMs, and vice versa.

InfiniBand SR-IOV Architecture Models—vSwitch with Prepopulated LIDs

In accordance with an embodiment, the present disclosure provides asystem and method for providing a vSwitch architecture with prepopulatedLIDs.

FIG. 5 shows an exemplary vSwitch architecture with prepopulated LIDs,in accordance with an embodiment. As depicted in the figure, a number ofswitches 501-504 can provide communication within the network switchedenvironment 500 (e.g., an IB subnet) between members of a fabric, suchas an InfiniBand fabric. The fabric can include a number of hardwaredevices, such as host channel adapters 510, 520, 530. Each of the hostchannel adapters 510, 520, 530, can in turn interact with a hypervisor511, 521, and 531, respectively. Each hypervisor can, in turn, inconjunction with the host channel adapter it interacts with, setup andassign a number of virtual functions 514, 515, 516, 524, 525, 526, 534,535, 536, to a number of virtual machines. For example, virtual machine1 550 can be assigned by the hypervisor 511 to virtual function 1 514.Hypervisor 511 can additionally assign virtual machine 2 551 to virtualfunction 2 515, and virtual machine 3 552 to virtual function 3 516.Hypervisor 531 can, in turn, assign virtual machine 4 553 to virtualfunction 1 534. The hypervisors can access the host channel adaptersthrough a fully featured physical function 513, 523, 533, on each ofhost channel adapters.

In accordance with an embodiment, each of the switches 501-504 cancomprise a number of ports (not shown), which are used in setting alinear forwarding table in order to direct traffic within the networkswitched environment 500.

In accordance with an embodiment, the virtual switches 512, 522, and532, can be handled by their respective hypervisors 511, 521, 531. Insuch a vSwitch architecture each virtual function is a complete virtualHost Channel Adapter (vHCA), meaning that the VM assigned to a VF isassigned a complete set of IB addresses (e.g., GID, GUID, LID) and adedicated QP space in the hardware. For the rest of the network and theSM (not shown), the HCAs 510, 520, and 530 look like a switch, via thevirtual switches, with additional nodes connected to them.

In accordance with an embodiment, the present disclosure provides asystem and method for providing a vSwitch architecture with prepopulatedLIDs. Referring to FIG. 5, the LIDs are prepopulated to the variousphysical functions 513, 523, 533, as well as the virtual functions514-516, 524-526, 534-536 (even those virtual functions not currentlyassociated with an active virtual machine). For example, physicalfunction 513 is prepopulated with LID 1, while virtual function 1 534 isprepopulated with LID 10. The LIDs are prepopulated in an SR-IOVvSwitch-enabled subnet when the network is booted. Even when not all ofthe VFs are occupied by VMs in the network, the populated VFs areassigned with a LID as shown in FIG. 5.

In accordance with an embodiment, much like physical host channeladapters can have more than one port (two ports are common forredundancy), virtual HCAs can also be represented with two ports and beconnected via one, two or more virtual switches to the external IBsubnet.

In accordance with an embodiment, in a vSwitch architecture withprepopulated LIDs, each hypervisor can consume one LID for itselfthrough the PF and one more LID for each additional VF. The sum of allthe VFs available in all hypervisors in an IB subnet, gives the maximumamount of VMs that are allowed to run in the subnet. For example, in anIB subnet with 16 virtual functions per hypervisor in the subnet, theneach hypervisor consumes 17 LIDs (one LID for each of the 16 virtualfunctions plus one LID for the physical function) in the subnet. In suchan IB subnet, the theoretical hypervisor limit for a single subnet isruled by the number of available unicast LIDs and is: 2891 (49151available LIDs divided by 17 LIDs per hypervisor), and the total numberof VMs (i.e., the limit) is 46256 (2891 hypervisors times 16 VFs perhypervisor). (In actuality, these numbers are actually smaller sinceeach switch, router, or dedicated SM node in the IB subnet consumes aLID as well). Note that the vSwitch does not need to occupy anadditional LID as it can share the LID with the PF

In accordance with an embodiment, in a vSwitch architecture withprepopulated LIDs, communication paths are computed for all the LIDsonce when the network is booted. When a new VM needs to be started thesystem does not have to add a new LID in the subnet, an action thatwould otherwise cause a complete reconfiguration of the network,including path recalculation, which is the most time consuming part.Instead, an available port for a VM is located (i.e., an availablevirtual function) in one of the hypervisors and the virtual machine isattached to the available virtual function.

In accordance with an embodiment, a vSwitch architecture withprepopulated LIDs also allows for the ability to calculate and usedifferent paths to reach different VMs hosted by the same hypervisor.Essentially, this allows for such subnets and networks to use aLID-Mask-Control-like (LMC-like) feature to provide alternative pathstowards one physical machine, without being bound by the limitation ofthe LMC that requires the LIDs to be sequential. The freedom to usenon-sequential LIDs is particularly useful when a VM needs to bemigrated and carry its associated LID to the destination.

In accordance with an embodiment, along with the benefits shown above ofa vSwitch architecture with prepopulated LIDs, certain considerationscan be taken into account. For example, because the LIDs areprepopulated in an SR-IOV vSwitch-enabled subnet when the network isbooted, the initial path computation (e.g., on boot-up) can take longerthan if the LIDs were not pre-populated.

InfiniBand SR-IOV Architecture Models—vSwitch with Dynamic LIDAssignment

In accordance with an embodiment, the present disclosure provides asystem and method for providing a vSwitch architecture with dynamic LIDassignment.

FIG. 6 shows an exemplary vSwitch architecture with dynamic LIDassignment, in accordance with an embodiment. As depicted in the figure,a number of switches 501-504 can provide communication within thenetwork switched environment 600 (e.g., an IB subnet) between members ofa fabric, such as an InfiniBand fabric. The fabric can include a numberof hardware devices, such as host channel adapters 510, 520, 530. Eachof the host channel adapters 510, 520, 530, can in turn interact with ahypervisor 511, 521, 531, respectively. Each hypervisor can, in turn, inconjunction with the host channel adapter it interacts with, setup andassign a number of virtual functions 514, 515, 516, 524, 525, 526, 534,535, 536, to a number of virtual machines. For example, virtual machine1 550 can be assigned by the hypervisor 511 to virtual function 1 514.Hypervisor 511 can additionally assign virtual machine 2 551 to virtualfunction 2 515, and virtual machine 3 552 to virtual function 3 516.Hypervisor 531 can, in turn, assign virtual machine 4 553 to virtualfunction 1 534. The hypervisors can access the host channel adaptersthrough a fully featured physical function 513, 523, 533, on each ofhost channel adapters.

In accordance with an embodiment, each of the switches 501-504 cancomprise a number of ports (not shown), which are used in setting alinear forwarding table in order to direct traffic within the networkswitched environment 600.

In accordance with an embodiment, the virtual switches 512, 522, and532, can be handled by their respective hypervisors 511, 521, 531. Insuch a vSwitch architecture each virtual function is a complete virtualHost Channel Adapter (vHCA), meaning that the VM assigned to a VF isassigned a complete set of IB addresses (e.g., GID, GUID, LID) and adedicated QP space in the hardware. For the rest of the network and theSM (not shown), the HCAs 510, 520, and 530 look like a switch, via thevirtual switches, with additional nodes connected to them.

In accordance with an embodiment, the present disclosure provides asystem and method for providing a vSwitch architecture with dynamic LIDassignment. Referring to FIG. 6, the LIDs are dynamically assigned tothe various physical functions 513, 523, 533, with physical function 513receiving LID 1, physical function 523 receiving LID 2, and physicalfunction 533 receiving LID 3. Those virtual functions that areassociated with an active virtual machine can also receive a dynamicallyassigned LID. For example, because virtual machine 1 550 is active andassociated with virtual function 1 514, virtual function 514 can beassigned LID 5. Likewise, virtual function 2 515, virtual function 3516, and virtual function 1 534 are each associated with an activevirtual function. Because of this, these virtual functions are assignedLIDs, with LID 7 being assigned to virtual function 2 515, LID 11 beingassigned to virtual function 3 516, and virtual function 9 beingassigned to virtual function 1 535. Unlike vSwitch with prepopulatedLIDs, those virtual functions not currently associated with an activevirtual machine do not receive a LID assignment.

In accordance with an embodiment, with the dynamic LID assignment, theinitial path computation can be substantially reduced. When the networkis booting for the first time and no VMs are present then a relativelysmall number of LIDs can be used for the initial path calculation andLFT distribution.

In accordance with an embodiment, much like physical host channeladapters can have more than one port (two ports are common forredundancy), virtual HCAs can also be represented with two ports and beconnected via one, two or more virtual switches to the external IBsubnet.

In accordance with an embodiment, when a new VM is created in a systemutilizing vSwitch with dynamic LID assignment, a free VM slot is foundin order to decide on which hypervisor to boot the newly added VM, and aunique non-used unicast LID is found as well. However, there are noknown paths in the network and the LFTs of the switches for handling thenewly added LID. Computing a new set of paths in order to handle thenewly added VM is not desirable in a dynamic environment where severalVMs may be booted every minute. In large IB subnets, computing a new setof routes can take several minutes, and this procedure would have torepeat each time a new VM is booted.

Advantageously, in accordance with an embodiment, because all the VFs ina hypervisor share the same uplink with the PF, there is no need tocompute a new set of routes. It is only needed to iterate through theLFTs of all the physical switches in the network, copy the forwardingport from the LID entry that belongs to the PF of the hypervisor—wherethe VM is created—to the newly added LID, and send a single SMP toupdate the corresponding LFT block of the particular switch. Thus thesystem and method avoids the need to compute a new set of routes.Further details of a vSwitch system and method supporting Dynamic LIDAssignment are described in Appendix A which is incorporated herein byreference.

In accordance with an embodiment, the LIDs assigned in the vSwitch withdynamic LID assignment architecture do not have to be sequential. Whencomparing the LIDs assigned on VMs on each hypervisor in vSwitch withprepopulated LIDs versus vSwitch with dynamic LID assignment, it isnotable that the LIDs assigned in the dynamic LID assignmentarchitecture are non-sequential, while those prepopulated in aresequential in nature. In the vSwitch dynamic LID assignmentarchitecture, when a new VM is created, the next available LID is usedthroughout the lifetime of the VM. Conversely, in a vSwitch withprepopulated LIDs, each VM inherits the LID that is already assigned tothe corresponding VF, and in a network without live migrations, VMsconsecutively attached to a given VF get the same LID.

In accordance with an embodiment, the vSwitch with dynamic LIDassignment architecture can resolve the drawbacks of the vSwitch withprepopulated LIDs architecture model at a cost of some additionalnetwork and runtime SM overhead. Each time a VM is created, the LFTs ofthe physical switches in the subnet can be updated with the newly addedLID associated with the created VM. One subnet management packet (SMP)per switch is needed to be sent for this operation. The LMC-likefunctionality is also not available, because each VM is using the samepath as its host hypervisor. However, there is no limitation on thetotal amount of VFs present in all hypervisors, and the number of VFsmay exceed that of the unicast LID limit. Of course, not all of the VFsare allowed to be attached on active VMs simultaneously if this is thecase, but having more spare hypervisors and VFs adds flexibility fordisaster recovery and optimization of fragmented networks when operatingclose to the unicast LID limit.

InfiniBand SR-IOV Architecture Models—vSwitch with Dynamic LIDAssignment and Prepopulated LIDs

FIG. 7 shows an exemplary vSwitch architecture with vSwitch with dynamicLID assignment and prepopulated LIDs, in accordance with an embodiment.As depicted in the figure, a number of switches 501-504 can providecommunication within the network switched environment 500 (e.g., an IBsubnet) between members of a fabric, such as an InfiniBand fabric. Thefabric can include a number of hardware devices, such as host channeladapters 510, 520, 530. Each of the host channel adapters 510, 520, 530,can in turn interact with a hypervisor 511, 521, and 531, respectively.Each hypervisor can, in turn, in conjunction with the host channeladapter it interacts with, setup and assign a number of virtualfunctions 514, 515, 516, 524, 525, 526, 534, 535, 536, to a number ofvirtual machines. For example, virtual machine 1 550 can be assigned bythe hypervisor 511 to virtual function 1 514. Hypervisor 511 canadditionally assign virtual machine 2 551 to virtual function 2 515.Hypervisor 521 can assign virtual machine 3 552 to virtual function 3526. Hypervisor 531 can, in turn, assign virtual machine 4 553 tovirtual function 2 535. The hypervisors can access the host channeladapters through a fully featured physical function 513, 523, 533, oneach of host channel adapters.

In accordance with an embodiment, each of the switches 501-504 cancomprise a number of ports (not shown), which are used in setting alinear forwarding table in order to direct traffic within the networkswitched environment 700.

In accordance with an embodiment, the virtual switches 512, 522, and532, can be handled by their respective hypervisors 511, 521, 531. Insuch a vSwitch architecture each virtual function is a complete virtualHost Channel Adapter (vHCA), meaning that the VM assigned to a VF isassigned a complete set of IB addresses (e.g., GID, GUID, LID) and adedicated QP space in the hardware. For the rest of the network and theSM (not shown), the HCAs 510, 520, and 530 look like a switch, via thevirtual switches, with additional nodes connected to them.

In accordance with an embodiment, the present disclosure provides asystem and method for providing a hybrid vSwitch architecture withdynamic LID assignment and prepopulated LIDs. Referring to FIG. 7,hypervisor 511 can be arranged with vSwitch with prepopulated LIDsarchitecture, while hypervisor 521 can be arranged with vSwitch withprepopulated LIDs and dynamic LID assignment. Hypervisor 531 can bearranged with vSwitch with dynamic LID assignment. Thus, the physicalfunction 513 and virtual functions 514-516 have their LIDs prepopulated(i.e., even those virtual functions not attached to an active virtualmachine are assigned a LID). Physical function 523 and virtual function1 524 can have their LIDs prepopulated, while virtual function 2 and 3,525 and 526, have their LIDs dynamically assigned (i.e., virtualfunction 2 525 is available for dynamic LID assignment, and virtualfunction 3 526 has a LID of 11 dynamically assigned as virtual machine 3552 is attached). Finally, the functions (physical function and virtualfunctions) associated with hypervisor 3 531 can have their LIDsdynamically assigned. This results in virtual functions 1 and 3, 534 and536, are available for dynamic LID assignment, while virtual function 2535 has LID of 9 dynamically assigned as virtual machine 4 553 isattached there.

In accordance with an embodiment, such as that depicted in FIG. 7, whereboth vSwitch with prepopulated LIDs and vSwitch with dynamic LIDassignment are utilized (independently or in combination within anygiven hypervisor), the number of prepopulated LIDs per host channeladapter can be defined by a fabric administrator and can be in the rangeof 0<=prepopulated VFs<=Total VFs (per host channel adapter), and theVFs available for dynamic LID assignment can be found by subtracting thenumber of prepopulated VFs from the total number of VFs (per hostchannel adapter).

In accordance with an embodiment, much like physical host channeladapters can have more than one port (two ports are common forredundancy), virtual HCAs can also be represented with two ports and beconnected via one, two or more virtual switches to the external IBsubnet.

Dynamic Reconfiguration with vSwitches

In accordance with an embodiment, the present disclosure provides asystem and method for dynamic network reconfiguration with vSwitches. Ina dynamic cloud environment, live migrations can be handled and can bescalable. When a VM is migrated and has to carry its addresses to thedestination, a network reconfiguration is necessary. Migration of thevirtual or alias GUIDs (vGUIDs), and consequently the GIDs, do not posesignificant burdens as they are high level addresses that do not affectthe underlying IB routing (e.g., linear forwarding tables and routes).For the migration of the vGUID, an SMP has to be sent to the destinationhypervisor in order to set the vGUID that is associated with theincoming VM, to the VF that will be assigned on the VM when themigration will be completed. However, migration of the LID is not sosimple, because the routes have to be recalculated and the LFTs of thephysical switches need to be reconfigured. Recalculation of the routesand distribution needs a considerable amount of time that lies in theorder of minutes on large subnets, posing scalability challenges.

In accordance with an embodiment, a vSwitch has the property that allVFs accessed through the vSwitch share the same uplink with the PF. Atopology agnostic dynamic reconfiguration mechanism can utilize thisproperty to make the reconfiguration viable on dynamic migrationenvironments. The LID reconfiguration time can be minimized byeliminating the path computation and reducing the path distribution. Themethod differs slightly for the two vSwitch architectures discussedabove (prepopulation of LIDs and dynamic LID assignment), but the basisis the same.

In accordance with an embodiment, the dynamic reconfiguration methodincludes two general steps: (a) Updating the LIDs in the participatinghypervisors: one Subnet Management Packet (SMP) is sent to each of thehypervisors that participate in the live migration, instructing them toset/unset the proper LID to the corresponding VF; and (b) Updating theLinear Forwarding Tables (LFTs) on the physical switches: one or amaximum of two SMPs are sent on one or more switches, forcing them toupdate their corresponding LFT entries to reflect the new position of amigrated virtual machine. This is shown more specifically below in theprocedures to migrate a virtual machine and reconfigure a network:

1: procedure UPDATELFTBLOCK(LFTBlock, Switch) 2:  // If the LFT blockneeds to be updated send SMP on the switch to 3:  // update theLFTBlock. When Swapping LIDs, 1 or 2 of all 4:  // the LFT Blocks mayneed to be updated per switch. When  copying 5:  // LIDs, only 1 of allthe LFT Blocks may need to be updated 6:  // per switch. 7:  if LFTBlockin Switch needs to be updated then 8:   Send SMP on Switch to updateLFTBlock 9:  end if 10: end procedure 11: procedureUPDATELFTBLocksONALLSWITCHES 12:  /* iterate through all LFTBlocks onall Switches 13:  *and update the LFTBlocks if needed. */ 14:  forLFTBlock in All_LFTBlocks do 15:   for sw in All_switches do 16:  UPDATELFTBLOCK(LFTBlock, sw) 17:   end for 18:  end for 19: endprocedure 20: procedure MIGRATEVM(VM, DestHypervisor) 21:  Detach IB VFfrom VM 22:  Start live migration of VM to the DestHypervisor 23:   /*Reconfiguration of the network is following */ 24:   // The migrationprocedure of the LID address slightly 25:   // differs in vSwitch withprepopulated LIDs and vSwitch   with dynamic LID assignment. 26:   /*Step described in Updating the LIDs in the participating   hypervisors*/ 27:   Migrate the IB addresses of VM 28:   /* Step described inUpdating the Linear Forwarding Tables   (LFTs) on the physical switches*/ 29:   UPDATELFTBLOCKONALLSWITCHES 30: end procedure 31: procedureMAIN 32:  MIGRATEVM(VM_to_be_Migrated, toHypervisor) 33: end procedureReconfiguration in vSwitch with Prepopulated LIDs

FIG. 8 shows an exemplary vSwitch architecture with prepopulated LIDsprior to a virtual machine migration, in accordance with an embodiment.As depicted in the figure, a number of switches 501-504 can providecommunication within the network switched environment 800 (e.g., an IBsubnet) between members of a fabric, such as an InfiniBand fabric. Thefabric can include a number of hardware devices, such as host channeladapters 510, 520, 530. Each of the host channel adapters 510, 520, 530,can in turn interact with a hypervisor 511, 521, and 531, respectively.Each hypervisor can, in turn, in conjunction with the host channeladapter it interacts with, setup and assign a number of virtualfunctions 514, 515, 516, 524, 525, 526, 534, 535, 536, to a number ofvirtual machines. For example, virtual machine 1 550 can be assigned bythe hypervisor 511 to virtual function 1 514. Hypervisor 511 canadditionally assign virtual machine 2 551 to virtual function 2 515, andvirtual machine 3 552 to virtual function 3 516. Hypervisor 531 can, inturn, assign virtual machine 4 553 to virtual function 1 534. Thehypervisors can access the host channel adapters through a fullyfeatured physical function 513, 523, 533, on each of host channeladapters.

In accordance with an embodiment, the virtual switches 512, 522, and532, can be handled by their respective hypervisors 511, 521, 531. Insuch a vSwitch architecture each virtual function is a complete virtualHost Channel Adapter (vHCA), meaning that the VM assigned to a VF isassigned a complete set of IB addresses (e.g., GID, GUID, LID) and adedicated QP space in the hardware. For the rest of the network and theSM (not shown), the HCAs 510, 520, and 530 look like a switch, via thevirtual switches, with additional nodes connected to them.

In accordance with an embodiment, each of the switches 501-504 cancomprise a number of ports (not shown), which are used in setting alinear forwarding table, such as linear forwarding table 810 associatedwith switch 501, in order to direct traffic within the network switchedenvironment 800. As shown in the figure, linear forwarding table 810forwards traffic addressed to virtual machine 2 551 (i.e., LID 3)through port 2 of switch 501. Likewise, because paths exist for all LIDseven if VMs are not running, the linear forwarding table can define aforwarding path to LID 12 through port 4 of switch 501.

FIG. 9 shows an exemplary vSwitch architecture with prepopulated LIDsafter a virtual machine migration, in accordance with an embodiment. Asdepicted in the figure, a number of switches 501-504 can providecommunication within the network switched environment 900 (e.g., an IBsubnet) between members of a fabric, such as an InfiniBand fabric. Thefabric can include a number of hardware devices, such as host channeladapters 510, 520, 530. Each of the host channel adapters 510, 520, 530,can in turn interact with a hypervisor 511, 521, and 531, respectively.Each hypervisor can, in turn, in conjunction with the host channeladapter it interacts with, setup and assign a number of virtualfunctions 514, 515, 516, 524, 525, 526, 534, 535, 536, to a number ofvirtual machines. For example, virtual machine 1 550 can be assigned bythe hypervisor 511 to virtual function 1 514. Hypervisor 511 canadditionally assign virtual machine 2 551 to virtual function 2 515, andvirtual machine 3 552 to virtual function 3 516. Hypervisor 531 can, inturn, assign virtual machine 4 553 to virtual function 1 534. Thehypervisors can access the host channel adapters through a fullyfeatured physical function 513, 523, 533, on each of host channeladapters.

In accordance with an embodiment, the virtual switches 512, 522, and532, can be handled by their respective hypervisors 511, 521, 531. Insuch a vSwitch architecture each virtual function is a complete virtualHost Channel Adapter (vHCA), meaning that the VM assigned to a VF isassigned a complete set of IB addresses (e.g., GID, GUID, LID) and adedicated QP space in the hardware. For the rest of the network and theSM (not shown), the HCAs 510, 520, and 530 look like a switch, via thevirtual switches, with additional nodes connected to them.

In accordance with an embodiment, each of the switches 501-504 cancomprise a number of ports (not shown), which are used in setting alinear forwarding table, such as linear forwarding table 910 associatedwith switch 501, in order to direct traffic within the network switchedenvironment 900.

In accordance with an embodiment, if virtual machine 2 551 needs to bemigrated from hypervisor 511 to hypervisor 531, and virtual function 3536 on hypervisor 531 is available, virtual machine 2 can be attached tovirtual function 3 536. In such a situation, the LIDs can swap (i.e.,the entry of the LID that is assigned to the migrating VM can be swappedwith the LID of the VF that is going to be used at the destinationhypervisor after the live migration is completed). The linear forwardingtable 910 on switch 501 can be updated as shown in the figure, namelythat traffic to LID 3 is now forwarded through port 4 (previously port2), and the path to LID 12 is now forwarded through port 2 (previouslyport 4).

In accordance with an embodiment, for vSwitch architecture withprepopulated LIDs, paths exist for all of the LIDs even if VMs are notrunning. In order to migrate a LID and keep the balancing of the initialrouting, two LFT entries on all switches can be swapped—the entry of theLID that is assigned to the migrating VM, with the LID of the VF that isgoing to be used at the destination hypervisor after the live migrationis completed (i.e., the virtual function that the migrating virtualmachine attaches to at the destination hypervisor). In referring againto FIGS. 7 and 8, if VM1 550 with LID 2 needs to be migrated fromhypervisor 551 to hypervisor 531, and VF3 536 with LID 12 on hypervisor531 is available and decided to be attached to the migrating virtualmachine 1 551, the LFTs of the switch 501 can be updated. Before themigration LID 2 was forwarded through port 2, and LID 12 was forwardedthrough port 4. After the migration LID 2 is forwarded through port 4,and LID 12 is forwarded through port 2. In this case, only one SMP needsto be sent for this update because LFTs are updated in blocks of 64 LIDsper block, and both LID 2 and 12 are part of the same block thatincludes the LIDs 0-63. If the LID of VF3 on hypervisor 531 was instead64 or greater, then two SMPs would need to be sent as two LFT blockswould have to be updated: the block that contains LID 2 (the VM LID) andthe block that contains the LID to be swapped that is bigger than 63.

Reconfiguration in vSwitch with Dynamic LID Assignment

In accordance with an embodiment, for the vSwitch architecture withDynamic LID assignment, the path of a VF follows the same path as thepath of the corresponding PF of the hypervisor where the VM is currentlyhosted. When a VM moves, the system has to find the LID that is assignedto the PF of the destination hypervisor, and iterate through all theLFTs of all switches and update the path for the VM LID with the path ofthe destination hypervisor. In contrast to the LID swapping techniquethat is used in the reconfiguration with prepopulated LIDs, only one SMPneeds to be sent at all times to the switches that need to be updated,since there is only one LID involved in the process.

Traditional Cost of Reconfiguration

In accordance with an embodiment, the time, RC_(t), needed for a fullnetwork re-configuration method is the sum of the time needed for thepath computation, PC_(I), plus the time needed for the LFTsDistribution, LFTD_(t), to all switches, as shown in equation 1:RC _(t) =PC _(t) +LFTD _(t)  (1)

In accordance with an embodiment, the computational complexity of thepaths is polynomially growing with the size of the subnet, and PC_(t) isin the order of several minutes on large subnets.

After the paths have been computed, the LFTs of the switches in anetwork, such as an IB subnet, can be updated. The LFT distribution timeLFTD_(t) grows linearly with the size of the subnet and the amount ofswitches. As mentioned above, LFTs are updated on blocks of 64 LIDs soin a small subnet with a few switches and up to 64 consumed LIDs, onlyone SMP needs to be sent to each switch during path distribution. Inother situations, where, such as a fully populated IB subnet with 49151LIDs consumed, 768 SMPs per switch are needed to be sent during pathdistribution in a traditional model.

The SMPs can use either directed routing or destination based routing.When using directed routing, each intermediate switch has to process andupdate the headers of the packet with the current hop pointer andreverse path before forwarding the packet to the next hop. In thedestination based routing, each packet is forwarded immediately.Naturally, directed routing can add latency to the forwarded packets.Nevertheless, directed routing is used by OpenSM for all traditionalSMPs. This is necessary for the initial topology discovery process wherethe LFTs have not been distributed yet to the switches, or when areconfiguration is taking place and the routes towards the switches arechanging.

Let n be a number of switches in the network; m the number of all LFTblocks that will be updated on each switch, determined by the number ofconsumed LIDs; k the average time needed for each SMP to traverse thenetwork before reaching each switch; and r the average time added foreach SMP due to the directed routing. Assuming no pipelining, the LFTdistribution time LFTD_(t) can be broken further down in equation 2:LFTD _(t) =n·m·(k+r)  (2)

By combining equations 1 and 2, equation 3 is a result for the timeneeded for a full network re-configuration:RC _(t) =PC _(t) +n·m·(k+r)  (3)

In large subnets, traditionally, the time needed for the pathcomputation, PC_(I), is much greater than the time needed for the LFTsdistribution, LFTD_(t), even though the LFTD_(t) becomes larger whenmore LIDs, and consequently more LFT blocks per switch m are used, andwhen more switches n are present in the network. The n·m part inequations 2 and 3 defines the total number of SMPs that needs to be sentfor the reconfiguration.

Reconfiguration Cost for Live Migration with vSwitch Architecture

Using traditional reconfiguration techniques would render VM migrationsunusable. In large subnets, the PC_(t) in equation 3 becomes very largeand dominates RC_(t). If a live migration triggered a full traditionalreconfiguration, it would generally take several minutes to complete.

In accordance with an embodiment, by utilizing the vSwitch withprepopulated LIDs or vSwitch with dynamic LID assignment, the PC_(t)portion of the reconfiguration time can be essentially eliminated sincethe paths are already calculated to swap or copy LID entries in the LFTof each switch. Furthermore, there is no need to send m SMPs per switch,because when a VM is migrated, only one or a maximum of two LIDs areaffected depending on which of the proposed vSwitch schemes is used,regardless of the total number of LFT blocks. As a result, only m′∈{1,2} SMPs are needed to be sent to the switches for each migration (m′=2if the two LID entries are not located in the same LFT block when theLIDs are prepopulated, otherwise m′=1). As well, there are certain casesthat 0<n′<n switches need to be updated.

In accordance with an embodiment, referring now to FIG. 10 which showsan exemplary vSwitch architecture with prepopulated LIDs with potentialvirtual machine migration paths, in accordance with an embodiment. Asdepicted in the figure, a number of switches 501-504 can providecommunication within the network switched environment 1000 (e.g., an IBsubnet) between members of a fabric, such as an InfiniBand fabric. Thefabric can include a number of hardware devices, such as host channeladapters 510, 520, 530. Each of the host channel adapters 510, 520, 530,can in turn interact with a hypervisor 511, 521, and 531, respectively.Each hypervisor can, in turn, in conjunction with the host channeladapter it interacts with, setup and assign a number of virtualfunctions 514, 515, 516, 524, 525, 526, 534, 535, 536, to a number ofvirtual machines. For example, virtual machine 1 550 can be assigned bythe hypervisor 511 to virtual function 1 514. Hypervisor 511 canadditionally assign virtual machine 2 551 to virtual function 2 515, andvirtual machine 3 552 to virtual function 3 516. Hypervisor 531 can, inturn, assign virtual machine 4 553 to virtual function 1 534. Thehypervisors can access the host channel adapters through a fullyfeatured physical function 513, 523, 533, on each of host channeladapters.

In accordance with an embodiment, the virtual switches 512, 522, and532, can be handled by their respective hypervisors 511, 521, 531. Insuch a vSwitch architecture each virtual function is a complete virtualHost Channel Adapter (vHCA), meaning that the VM assigned to a VF isassigned a complete set of IB addresses (e.g., GID, GUID, LID) and adedicated QP space in the hardware. For the rest of the network and theSM (not shown), the HCAs 510, 520, and 530 look like a switch, via thevirtual switches, with additional nodes connected to them.

In accordance with an embodiment, each of the switches 501-504 cancomprise a number of ports (not shown), which are used in setting alinear forwarding table, such as linear forwarding table 1010 associatedwith switch 501, in order to direct traffic within the network switchedenvironment 1000.

In accordance with an embodiment, FIG. 10 depicts a situation in anetwork switched environment 1000 where VM2 551 can potentially migratefrom hypervisor 511 to hypervisor 521 (where there are three availablevirtual functions). If LID 3 was swapped with any of the available LIDsin hypervisor 521 (6, 7 or 8), then the switch 501 would not need to beupdated at all, because the initial routing already routes LID 3 andLIDs 6, 7 and 8 share the same port (port 2) on switch 501. Inparticular for this example n′=1, because only the switch 503 (i.e., aleaf switch) would need to be updated.

In accordance with an embodiment, eventually, the cost vSwitch RC_(t) ofthe disclosed reconfiguration mechanism is found in equation 4, and inlarge subnets, vSwitch RC_(t) is much less than RC_(t).vSwitch_RC _(t) =n′·m′·(k+r)  (4)

In accordance with an embodiment, destination based routing for the SMPpackets can be used. When VMs are migrated, the routes for the LIDsbelonging to switches will not be affected. Therefore, destination basedrouting can guarantee proper delivery of SMPs to the switches and r canbe eliminated from equation 4, giving equation 5:vSwitch_RC _(t) =n′·m′·k  (5)

In accordance with an embodiment, pipelining can be used to even furtherreduce the vSwitch reconfiguration time.

FIG. 11 is a flow chart of a method for supporting virtual machinemigration in a network, in accordance with an embodiment. At step 1110,the method can provide, at one or more computers, including one or moremicroprocessors, one or more switches, the one or more switchescomprising at least a leaf switch, wherein each of the one or moreswitches comprise a plurality of ports, a plurality of host channeladapters, wherein each of the host channel adapters comprises at leastone virtual function, and wherein the plurality of host channel adaptersare interconnected via the one or more switches, a plurality ofhypervisors, wherein each of the plurality of hypervisors are associatedwith at least one of the plurality of host channel adapters, and aplurality of virtual machines, wherein each of the plurality of virtualmachines are associated with at least one virtual function.

At step 1120, the method can arrange the plurality of host channeladapters with one or more of a virtual switch with prepopulated localidentifiers (LIDs) architecture or a virtual switch with dynamic LIDassignment architecture.

At step 1130, the method can live migrate a first virtual machine of theplurality of virtual machines running on a first hypervisor of theplurality of hypervisors to a second hypervisor of the plurality ofhypervisors; and wherein the first hypervisor is associated with a firsthost channel adapter of the plurality of host channel adapters, and thesecond hypervisor is associated with a second host channel adapter ofthe plurality of host channel adapters.

The present invention may be conveniently implemented using one or moreconventional general purpose or specialized digital computer, computingdevice, machine, or microprocessor, including one or more processors,memory and/or computer readable storage media programmed according tothe teachings of the present disclosure. Appropriate software coding canreadily be prepared by skilled programmers based on the teachings of thepresent disclosure, as will be apparent to those skilled in the softwareart.

In some embodiments, the present invention includes a computer programproduct which is a storage medium or computer readable medium (media)having instructions stored thereon/in which can be used to program acomputer to perform any of the processes of the present invention. Thestorage medium can include, but is not limited to, any type of diskincluding floppy disks, optical discs, DVD, CD-ROMs, microdrive, andmagneto-optical disks, ROMs, RAMs, EPROMs, EEPROMs, DRAMs, VRAMs, flashmemory devices, magnetic or optical cards, nanosystems (includingmolecular memory ICs), or any type of media or device suitable forstoring instructions and/or data.

The foregoing description of the present invention has been provided forthe purposes of illustration and description. It is not intended to beexhaustive or to limit the invention to the precise forms disclosed.Many modifications and variations will be apparent to the practitionerskilled in the art. The embodiments were chosen and described in orderto best explain the principles of the invention and its practicalapplication, thereby enabling others skilled in the art to understandthe invention for various embodiments and with various modificationsthat are suited to the particular use contemplated. It is intended thatthe scope of the invention be defined by the following claims and theirequivalents.

What is claimed is:
 1. A system for supporting virtual machine livemigration in a subnet, comprising: one or more microprocessors; aplurality of switches, wherein each of the plurality of switchescomprises a plurality of ports and a linear forwarding table (LFT); aplurality of host channel adapters, each comprising a virtual function,a virtual switch, and a physical function, wherein each virtual functionis assigned a local identifier (LID) of a plurality of LIDs; a pluralityof hypervisors, each hypervisor being associated with at least one hostchannel adapter of the plurality of host channel adapters; and a virtualmachine, the virtual machine being associated with a first virtualfunction of a first host channel adapter; wherein the virtual machine isaddressed within the subnet via a first LID assigned to the firstvirtual function; wherein the virtual machine operates to perform a livemigration to a second virtual function of a second host channel adapter,the second virtual function being assigned a second LID; wherein uponthe virtual machine performing the live migration, the first virtualfunction is assigned the second LID, and the second virtual function isassigned the first LID.
 2. The system of claim 1, wherein upon the firstvirtual machine performing the live migration, a first linear forwardingtable of a switch of the plurality of switches is updated.
 3. The systemof claim 2, wherein the update comprises a swapping of at least twoentries within the linear forwarding table, a first entry of the atleast two entries being associated with the first LID, and a secondentry of the at least two entries being associated with the second LID.4. The system of claim 1, wherein each of the plurality of hypervisorsis configured to access an associated host channel adapter through thephysical function.
 5. The system of claim 1, wherein each of theplurality of virtual functions operates as a virtual Host ChannelAdapter (vHCA).
 6. The system of claim 5, wherein prior to the migrationof the virtual machine, a first hypervisor of the plurality ofhypervisors assigns the virtual machine to the first virtual function.7. The system of claim 5, wherein after the migration of the virtualmachine, a second hypervisor of the plurality of hypervisors assigns thevirtual machine to the second virtual function.
 8. A method forsupporting virtual machine live migration in a subnet, comprising:providing, at a computer including one or more microprocessors; aplurality of switches, wherein each of the plurality of switchescomprises a plurality of ports and a linear forwarding table (LFT); aplurality of host channel adapters, each comprising a virtual function,a virtual switch, and a physical function, wherein each virtual functionis assigned a local identifier (LID) of a plurality of LIDs; a pluralityof hypervisors, each hypervisor being associated with at least one hostchannel adapter of the plurality of host channel adapters; and a virtualmachine, the virtual machine being associated with a first virtualfunction of a first host channel adapter; addressing the virtual machinewithin the subnet via a first LID assigned to the first virtualfunction; live migrating the virtual machine to a second virtualfunction of a second host channel adapter, the second virtual functionbeing assigned a second LID; upon the virtual machine performing thelive migration, assigning the first virtual function the second LID; andassigning the second virtual function the first LID.
 9. The method ofclaim 8, wherein upon the first virtual machine performing the livemigration, a first linear forwarding table of a switch of the pluralityof switches is updated.
 10. The method of claim 9, wherein the updatecomprises a swapping of at least two entries within the linearforwarding table, a first entry of the at least two entries beingassociated with the first LID, and a second entry of the at least twoentries being associated with the second LID.
 11. The method of claim 8,wherein each of the plurality of hypervisors is configured to access anassociated host channel adapter through the physical function.
 12. Themethod of claim 8, wherein each of the plurality of virtual functionsoperates as a virtual Host Channel Adapter (vHCA).
 13. The method ofclaim 12, wherein prior to the migration of the virtual machine, a firsthypervisor of the plurality of hypervisors assigns the virtual machineto the first virtual function.
 14. The method of claim 12, wherein afterthe migration of the virtual machine, a second hypervisor of theplurality of hypervisors assigns the virtual machine to the secondvirtual function.
 15. A non-transitory computer readable storage mediumhaving instructions thereon for supporting virtual machine livemigration in a subnet, which when read and executed by a computer causethe computer to perform steps comprising: providing, at a computerincluding one or more microprocessors; a plurality of switches, whereineach of the plurality of switches comprises a plurality of ports and alinear forwarding table (LFT); a plurality of host channel adapters,each comprising a virtual function, a virtual switch, and a physicalfunction, wherein each virtual function is assigned a local identifier(LID) of a plurality of LIDs; a plurality of hypervisors, eachhypervisor being associated with at least one host channel adapter ofthe plurality of host channel adapters; and a virtual machine, thevirtual machine being associated with a first virtual function of afirst host channel adapter; addressing the virtual machine within thesubnet via a first LID assigned to the first virtual function; livemigrating the virtual machine to a second virtual function of a secondhost channel adapter, the second virtual function being assigned asecond LID; upon the virtual machine performing the live migration,assigning the first virtual function the second LID; and assigning thesecond virtual function the first LID.
 16. The non-transitory computerreadable storage medium of claim 15, wherein upon the first virtualmachine performing the live migration, a first linear forwarding tableof a switch of the plurality of switches is updated.
 17. Thenon-transitory computer readable storage medium of claim 16, wherein theupdate comprises a swapping of at least two entries within the linearforwarding table, a first entry of the at least two entries beingassociated with the first LID, and a second entry of the at least twoentries being associated with the second LID.
 18. The non-transitorycomputer readable storage medium of claim 15, wherein each of theplurality of hypervisors is configured to access an associated hostchannel adapter through the physical function.
 19. The non-transitorycomputer readable storage medium of claim 15, wherein each of theplurality of virtual functions operates as a virtual Host ChannelAdapter (vHCA).
 20. The non-transitory computer readable storage mediumof claim 19, wherein prior to the migration of the virtual machine, afirst hypervisor of the plurality of hypervisors assigns the virtualmachine to the first virtual function.